7. ET: muscle

Question 1

why does anaerobic respiration become inefficient after ~30s and have a max duration of 120s?

Answer 1

metabolites like lactic acid and lead to H+ buildup, causing high pH in cells, which leads to poor cell function

Question 2

what lasts longer - a muscle twitch or an action potential. why?

Answer 2

muscle twitch lasts 100ms, while AP lasts 1.
because calcium handling that regulates a muscle twitch takes much less time than process of AP generation.

Question 3

which type of muscle fibre is smallest? why?

Answer 3

type 1. it is smaller to maximise surface area for diffusion of oxygen to support aerobic respiration, its primary ATP generation pathway.

Question 4

compare the two types of muscle fibres/motor units
(ATP pathway, size, organelles and nutrients, glycolysis, who might have lots)

Answer 4

type 1 - slow twitch.
utilise aerobic respiration, smaller to maximise SA, lots of mitochondria and high blood supply, moderate glycolytic ability, lots found in marathon runners.
type 2 - fast twitch.
utilise anaerobic respiration, larger, less mitochondria and lower blood supply, high glycolytic ability, lots found in powerlifters or sprinters.

Question 5

what happens to motor unit recruitment as tension increases

Answer 5

more units will be increased, and the type changes from initially smaller more fatigue resistant fibres to larger fibres.

Question 6

what does tetanus infection do to the body, what does treatment involve

Answer 6

suppresses inhibiting action on motor neuron activity, resulting in constant tetanic contraction throughout the whole body, including the diaphragm.
treatment involves neuromuscular blockers and ventilation

Question 7

why does overstretched sarcomere length generate less active tension

Answer 7

as there is less filament overlap, so less myosin heads can bind actin/less cross bridges formed

Question 8

what is/causes a complete/fused tetanus

Answer 8

a complete tetanus occurs when muscle is stimulated so rapidly that it does not relax at all, causing a constant high tension peak

Question 9

what is a tetanus

Answer 9

a state of sustained muscle contraction caused by repeated low frequency stimulation of the muscle fibres

Question 10

what is/causes an incomplete/unfused tetanus

Answer 10

an incomplete tetanus occurs when muscle is stimulated again before completely relaxing, increasing tension in peals

Question 11

what are the two factors regulation of force is dependent on

Answer 11

rate of stimulation and recruitment

Question 12

what is in a motor unit

Answer 12

a motor neuron and all the muscle fibres it innervates

Question 13

what is passive force/tension

Answer 13

force that increases as the muscle is stretched, occurring irrespective of stimulus, due to passive, non-contractile, elastic elements (mainly titin, also cell membrane)

Question 14

what is active force/tension

Answer 14

force developed by cross-bridge cycling, dependent on overlap of myosin and actin

Question 15

what sarcomere length is optimal for active tension and why

Answer 15

2-2.2 uM (micrometers), as all myosin heads can be bound to an actin binding site

Question 16

why does understretched sarcomere length generate less active tension

Answer 16

thin filaments are overlapped this filaments can collide interfere; myosin can bind the wrong actin filament

Question 17

what is a premature contraction in cardiac myocytes

Question 18

what is the DHPR - difference in its action in skeletal and cardiac muscle

Question 19

what is the differing effect of effect of amount of Ca2+ release in cardiac and skeletal muscle

Question 20

AP length in cardiac myocytes